I just put my motor back together after installing a new lower intake manifold gasket, and have a serious problem.

After starting, the engine redlined itself until there was a loud pop and governor killed it. I smelled something burning at this point. After a few more tries, the engine finally idled on its own but it was sputtering badly. The burning smell was gone, and when you revved it up it seemed to run OK but would not hold stable RPMs. Even now, it sometimes starts and revs up or it starts and lets off a loud pop before giving up. When I opened my oil filler cap, I did notice some blue smoke.

I thought that I did everything properly, torquing the rocker arm and manifold bolts to spec and marking the placement of the pushrods, etc. I checked my wiring and don't see anything obviously unplugged....

What do you guys think? Is there something simple that I could have forgotten or did I royally screw up and bend a valve?